Blend of plastics with wood particles

ABSTRACT

According to the invention blends of wood particles and plant particles and plastic are generated in an extruder thereby that the plastic is converted separately into a liquid melt before the joining takes place.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of PCT InternationalApplication No. PCT/EP2007/009140 filed on Oct. 22, 2007 (anddesignating the United States), an application which itself claimspriority to European Patent Application No. 07020157.9 filed on Oct. 15,2007 and German Patent Application No. 102006054204.5 filed on Nov. 15,2006.

FIELD OF THE INVENTION

The invention concerns the blend of plastics with wood particles orother plant particles or the like. As far in the following only wood oronly wood particles are mentioned, then this includes other plants andplant particles.

BACKGROUND OF THE INVENTION

Plastics are used in manifold applications

-   -   molded parts, work pieces, blocks, boards, films, webs,        coatings, tubes, hoses, bars, rods, profiles, bands, strings,        wires, bristles, grids, adhesives, lacquers, glues, pastes,        mastics, binders,    -   colours, plasters, spittle, casting compounds, sealing masses,        melt and coating materials, gels,    -   filaments, brins, threads, silks, strands, mats, fleeces,        fabrics

Plastics can consist of monomers and/or polymers. Often it is a blend,whereas also blends of other materials than plastics are found. Thisapplies especially for the production of plastic foam.

For the compounding of plastics the use of extruders is preferred.

By means of an extruder the used material can be very well melted, mixedand homogenized and dispersed respectively.

Moreover, the used material can simultaneously be heated or cooled. Forheating or cooling there are heating and cooling lines in the extrudershell and, where necessary, in the spindles. In addition, thedeformation of the used material performed by the extruder spindlescauses a considerable heating.

Very difficult materials can be blended in the extruder. Wood andplastics are belonging to the materials difficult to blend. Thereby thewood is supplied in small particles into the extruder and there wrappedwith plastic. In order to provoke the wrapping the plastic must beplasticised. This happens under corresponding heating and underpressure. However, the heat is only very badly transported by the wood.Moreover, the wood is very porous. As per an older proposal there mightbe the danger that the plastic will be pressed disproportionately intothe pores and will be unevenly distributed and no all-sided wrapping ofthe wood particles will take place.

The wool-plastic blend is also described as wood substitute.

Wood is used in several fields of application. Furniture, interiorfittings, trade fair construction, even automotive linings.

With regard to the furniture you have to distinguish between furniturewhere wood is only construction material and furniture where wood isused as visible surface.

For upholstered furniture wood is mostly used as construction material.

Generally all upholsteries have a solid substructure, e.g. a frame, alsocalled rack. In and at the rack there are optionally mounted seats,backrests and armrests as well as feet.

Optionally the rack forms also directly the seat, backrests and armrestsor vice versa. The material out of which the rack is produced is theconstruction material.

Traditionally the frames for upholsteries are produced of wood. Boardsand sticks are used. Wood has the advantage that the single parts can beconnected with each other as well as with the upholstery and theupholstery cover by the so-called stapling. For the stapling u-shapedfasteners are used. The fastener replaces the bullen-nails of the formerdays.

Other furniture show the wood as visible, decoration or ornament areasrespectively.

To some extent only specific rare kinds of wood fulfill the requestedrequirements for this. Rare lumber is relatively expensive. Since longit is therefore state of the technology to cut veneers out of rare woodwhich forms the visible surface. Veneers comprise thin, filmy woodcuts.A considerable waste occurs when the veneers shall be processed like thewood is grown.

By the blend of wood and plastic an advantageous wood substitute occurs.

Instead of wood also other comminuted plants can be used. Optionally anextrudate is generated from plastic and wool and other additives, whichis foamed or unfoamed. At low wood proportion in the extrudate you speakof an armouring or about the use of wood as filler. In the USA you speakof a wood substitute if the wood proportion in the blend has reached aweight proportion of 50%. For example, boards made of the blend of wooland plastic with the indicated blending proportion are common practicein the USA. The US-market accepts this. An example for the blends usualin the USA shows the WO 02/103113A.

The European market only accepts a wool substitute in the visible areaonly, if the appearance of the material is essentially similar to wood.Thereby 70% and more of wood are required.

However, an enduring outdoor application free of defects could up to nownot be reached with such a material.

For the use of other plant components, e.g. straw instead of wood issimilar with the wood. To some extent the plant part have a lowerstability than wood. As far as the stability is concerned the blend mustbe changed accordingly. As further plant components also grain grist andcomminuted hay can be used.

As per an older proposal the plastic proportion of the extrudate shallbe reduced as far as possible. Thereby wood proportions at the extrudateof 60 to 95 wght % referred to the blend are aimed for. The optimalplastic proportion shall be added against the blend proportions, theprocessing and the intended characteristic values of the blend.

As per the older proposal the dimensions of the plant particles aredestined by the traversing of the particles in the extruder when usingtraditional extruders. Thereby the traversing is determined by theclearance of the moving extruder parts in the extruder and by theopening width of the die gap. The traversing can be determined by meansof the known machine data. Then the dimensions of the plant particles,admissible for the respective extruder, can be determined. For safetyreasons, you can choose smaller dimensions of the plant particles thanthe above described traversing.

Alternatively, as per the older proposal the traversing of the extrudercan be adjusted to the requested particle size. This is done by means ofthe new construction of the extruder or the exchange of constructionparts, e.g. the exchange of the extruder screw, the die or the liner inthe extruder housing. Modern extruders have a liner in the extruderhousing, in which the screws are rotating.

As plastics all extrudable plastics can be considered, especiallyPolyethylene (PE), Polystyrene (PS), Polyurethane (PU) and Polypropylene(PP). Especially preferred is the use of PE.

The bonding agents can compensate a lack of adhesion of plastics withplant particles and wood respectively.

Bonding agents generate molecular bridges at the interfaces between thematerials to be connected, here the plastic.

As far as also other fillers or armouring materials/reinforcing agentslike e.g. glass fibers are used, the bonding agents can also have thetask to increase the adhesion to these other materials. Bonding agentscan be VC (vinyl chloride)-copolymers, phenolic resins, cautchoucderivates or acrylic resins without or with PF (phenol-formaldehyde)-and EP(epoxy)-resins.

As bonding agents are known generally also EVA (ethylene-vinylacetate-copolymers; It might also already be sufficient to make theplant particles water-repellent, i.e. to decrease the surface tension.

Traditionally the plastic is supplied as granulate with plant particlesand additives into the extruder. Optionally the granulates containalready a blend of plastic and additives.

By means of drying the humidity can be reduced to every degree requiredfor the extrusion. Not always a minimal degree of humidity is required,but optionally a destined moisture content by which you can influencethe extrusion process and/or the condition of the extrudate.

So far, twin-screw extruders have been regarded as especially favourablebecause these extruders have:

-   -   a very high feed effect    -   a very good pressure build-up.

Advantageously, extruders from different elements and section ofdifferent kind of construction respectively can be assembled. Thereforeit is possible to insert for the plasticising zone an element in theconstruction type of a twin-screw extruder, being advantageous there,and to combine this element in other extruder zones with other kinds ofconstruction, having there advantages. Thus, a single-screw extrudersection can be used in the feeding zone with which the pressure build-upcan be presented advantageously. For the blend and homogenization othersections will be better.

Under pressure and temperature the plastic is melting. In the furtherstep of the blend used through the extruder the blend will behomogenized. For the homogenization zone and the dispersion zone it isof advantage to us there extruder elements having a high mixingcapacity. These are for example elements in the design of a planetaryroller extruder. This element has simultaneously a high cooling effectby which the processing temperature can be controlled very exactly.Depending on type of plant and type of wood respectively and dependingon the plastic an optimal processing temperature for the melt isresulting. The temperature can e.g. amount up to 200° C. at a max. dwelltime (temperature loading time) of 15 min. At a shorter duration themax. temperature can be higher than at a longer duration.

At the further extrusion a differentiation must be made between theextrusion of unfoamed plastic and the extrusion of foamed plastic.

The residual moisture can serve as lubricant. The residual moisture canalso enter into chemical reaction. For example the moisture can enterinto reaction with the lignin of the plant particles. Surprisingly anameliorated adhesion between wood and plastic can be caused by this. Theadequate content of moisture/lignin can be tested by variation of themoisture and variation of the lignin content. Lignin is also availablein customary liquid form.

In case no water is desired at the extrusion, this can be counteractedby drying of the plant particles before the extrusion. In addition orinstead of the drying the moisture can be eliminated after thevaporization in the extruder by means of the degassing. The degassingcan occur immediately after the vaporization. This takes place regularlyin the plasticization zone. There the necessary heating takes place.This heating results from the forming works during plasticization and,if necessary, by supply of heat. The heat supply can take place e.g. viaa heating-cooling system in the extruder housing.

The degassing takes place, if requested, latest directly in front of theextrusion die.

The degassing requires that the melt pressure will be reduced.

Known is also the degassing by use of two extruders in tandemarrangement at the transfer between the two extruders.

The degassing can also take place in one extruder. The necessarypressure reduction in the melt can be carried out by different measures,e.g. by change of the pitch of the screw in the extruder.

For the degassing the melt can also be taken-off out of the extruder andled via a degassing device and returned again into the extruder.

By this, the pressure control can be essentially made easier byinterconnection of a melt pump. This is valid also for the pressuredirectly in front of the extrusion die (tool). Here the pressure can bekept additionally constant by means of the melt pump and thus thequality of the extrudate can be improved.

The higher the wool proportion in the blend, the bigger is the dangerthat the material will be no longer suitable for an outdoor application.The known materials decompose after some time due to steady changes offreeze/thaw. A further disadvantage of the known materials adisproportionate swelling which easily leads to bigger damages or forwhich oversized expansion joint must be considered.

Moreover, the wear of the extrusion line will be increased with anincreasing wood proportion.

The wear reduces the efficiency of the line.

Therefore, the invention made it is business to improve the productionof wood substitute made of a blend of wood particles or other plantparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an exemplary extruder for theproduction of blends of wood particles and plastic in accordance withthe present invention;

FIG. 2 is a partial cross-sectional view of the exemplary extruder ofFIG. 1;

FIG. 3 is another partial cross-sectional view of the exemplary extruderof FIG. 1;

FIG. 4 is yet another partial cross-sectional view of the exemplaryextruder of FIG. 1;

FIG. 5 is a partial cross-sectional view of another exemplary extruderin accordance with the present invention;

FIG. 6 is another view of the exemplary extruder of FIG. 5;

FIG. 7 is yet another partial cross-sectional view of the exemplaryextruder of FIG. 5;

FIG. 8 is a view of an exemplary line for the production of blends ofwood particles and plastic in accordance with the present invention;

FIG. 9 is another view of the exemplary line for the production ofblends of wood particles and plastic of FIG. 8;

FIG. 10 is yet another view of the exemplary line for the production ofblends of wood particles and plastic of FIG. 8; and

FIG. 11 is a cross-sectional view of an intermediate ring for theexemplary line for the production of blends of wood particles andplastic of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

Especially the following shall be achieved:

the production of materials with a better wood impression, an outdoorapplication of the materials should be possible, and the efficiency ofthe line shall be improved by decreasing of the wear. As far as in thefollowing wood is mentioned this includes the above mentionedalternative plant particles. The desired better wood impression incomparison to the US-standard required wood proportions and plantproportions respective of min. 60 wght %, preferably 65 wght % and more.

Due to the invention, an essential process improvement will be reachedby means of a blend of plastic and wood particles and other plantparticles in a planetary roller extruder or planetary roller extrudersection.

This application is simultaneously opposed to the awareness that highwood proportions and high plant proportions respectively lead to anintense wear in the intended planetary roller extruder or planetaryroller extruder section.

Preferably the wear will be reduced in that way that the plastic willbe—at least separated from wood and optionally also separated from otherwear causing additives of the blend—plasticized and afterwards injectedinto the flow of the wood particles and that the blend will behomogenized and pressed.

To the additives can belong among others: colours, couplers for increaseof the adhesion between plastic and wood, lubricants for reduction ofthe friction in the extruder, water repellents, stabilizers.

In the U.S. Pat. No. 6,479,002B1 is mentioned among others that theplastic will be melted separated from wood particles and other plantparticles and afterward supplied to the wood particles and other plantparticles. But this is not intended as solution at planetary rollerextruders. Aim of this measure is to gain time which otherwise isnecessary for the melting of the plastic. In this US patentspecification the extruder is needed in its whole length in order tocause in a steadily repeated pressure build-up and subsequentdecompression a drying of the wood and the plant particles respectively.Thereby an evaporation of the excessive water content takes place.Afterwards the water vapour shall be sucked off. The suction calls for adecrease of pressure and the use of a suction draught.

Thereby it is intended to repeat the pressure build-up withdecompression so often until the required drying has been reached.

The areas of the pressure build-up and the decompression can be seenfrom the drawing without further ado. There are changing areas of highpitch with areas of low pitch. At the same time an intensive blending ofwood and plastic shall take place. For this a counterrotating twin-screwextruder is intended. Twin-screw extruders are marked by a high pressurebuild-up and by a high mixing effect.

This concept cannot be transposed with a planetary roller extruderaccording to the invention. The intended toothing in the planetaryroller extruder normally has a constant pitch over the whole length.This is opposed to the concept of changing pitch.

The use of planetary roller extruders for the production of blends ofwood and plastic itself is known. This, however, is limited until thepriority date of the application at hand to written considerationsconcerning the use of planetary roller extruders. Such considerationscan be found for example in the following prints: DE 102004005058, DE102004005034, DE 10310510, DE 10228191. All these proposals have incommon that they did not become practical relevance. This is traced backto the fact the traversing of wood particles in a larger quantity in aplanetary roller extruder is very difficult. This is especially validwhen exceeding the limit according to the invention of 60 wght %,especially of 65 wght %. Then there exists the risk that the particleswill be milled into the toothing by the rotating planets and will bebuilt up on the tooth root surface. Then the particles will no longer bedisplaced from the tooth root surface of the central spindle and thetooth root surface of the toothing of the housing by the teeth of theplanetary spindles. This is also valid for the particles in the toothroot surface of the toothing of the planetary spindles.

Due to the build-up of the particles in the tooth root surface askipping over of the planets will arise which are kept during theirrotation only in the toothing of the central spindle and in the toothingof the surrounding housing. At the skipping the whole toothing will bedamaged. The consequence will be a total loss with correspondingoperating failure for the repair. Independent of the risk of damage theplant particles cause a considerable wear at the planetary rollerextruder by the build-up of particles in the tooth root surface. Now,the costs for a planetary roller extruder are much higher than the costsfor single-screw extruders and twin-screw extruders. Therefore, theabove considerations for the design of an extrusion line for theproduction of blends of wood and plastic could not be realized forreasons of acquisition cost for a planetary roller extruder.

All lines known in practice are using twin-screw extruders.

An example for this is also the line for the production of blends ofwood and plastic describes in WO 02/103113.

According to the invention the acquisition cost will be reduced therebythat a planetary roller extruder will be used which supplies thewood/plant-plastic blend to several downstream single-screw extruders.Each of these single-screw extruders has the only purpose to secure thenecessary pressure for a passage of the blend through the downstreamdie. By its outlet cross section the die defines the cross section ofthe outcoming strand. Thereby the same or different dies can be used.According to this different extruders form parallel production lineswhich are served from a joint line component with the described blend.Instead of the single-screw extruder also other extruders could be usedsingly or several other extruders could be used. The single-screwextruders, however, are unrivalled favourable and fulfill all describedconditions.

The acquisition cost of the joint planetary roller extruder aredistributed to all production lines and therefore the full impact is notto great than at the us of an independent planetary roller extruder forevery production line.

Preferably the distribution of the blend is used in order to carry out adegassing over the section. The degassing can take place at the ambientair. The heat contained in the blend provokes already a degassing. Thedegassing can be increased by application of vacuum.

The degassing at the outlet of the planetary roller extruder can be thesole degassing place or can be completes with a known degassing atanother place of the planetary roller extruder.

Optionally a storage container is intended behind the planetary rollerextruder. The storage container forms a buffer by balancing fluctuationsin production between the planetary roller extruder and the downstreamproduction lines.

In the storage container the blend is kept on the intended temperature.Preferably, also in the storage container a degassing takes place.

The distributor can have different forms.

One alternative is formed by a switch extending like a knife into theapproaching blend and diverting the requested quantity from the flow. Byadjustment of the switch the diverted quantity can be altered.Preferably the adjustment of the switch is combined with a flowmeteringso that a contact for an adjustment of the switch is given at anundercut or excess of the requested quantity. Preferably this regulationis provided with a special inertia so that not every small cavityimmediately leads to an adjustment of the switch. The inertia of theregulation can be achieved thereby that it is measured in temporalintervals. The intervals have at least a length of 5 seconds, preferablya length of 10 seconds, still more preferred a length of min. 20seconds. The inertia of the regulation can also be achieved thereby thatthe adjustment only reacts when achieving larger deviations from the setvalue. Preferably a reaction is intended at a deviation from the targetquantity of mind. 5 wght %, still more preferred at a deviation of min.10 wght % and highly preferred at a deviation of min. 20 wght %.

At two branches to two production lines one switch will be sufficient.

At three branches to three production lines two switches will besufficient.

At four branches to four production lines three switches will besufficient.

The number of the switches is by 1 smaller than the number of branches.

Optionally the switches are combines with an open chute. Preferable thechute has therefore a smooth floor so that the switches can be movedslightly above the floor or even when contacting the floor.

The switches are designed jointed and equipped with a servomotor.

The quantity measurement is executed optionally in the range of the feedopening or feed hopper at the downstream single-screw extruders.

The quantity measurement can also be executed in the way of a weightmeasurement at the chute. For this preferably directly behind theswitches there is arranged resiliently a part of the branch and is thereequipped with a measuring device. Thereby electrically effecting loadcells can be concerned. Such load cells have a strain gauge which reactsto different loads e.g. with different resistance to an electricalcurrent flowing through.

The interval regulation can also be combined with the described lagerquantity deviation.

Preferably the set values of the regulation can be altered in order toallow for an adjustment of different required quantities of blends inthe production lines. The required quantities of blends in theproduction lines are changing e.g. when other profiles of smaller crosssections or larger cross sections shall be produced.

The distributor can also have a distributor cone which guides the blendcoming out of the extruder into a chute. From the chute there are goingdifferent branches to the downstream production lines. The distributorcone can guide the blend also directly into the branches. Then thedifferent branches are arranged preferably around the distributor cone.

Optionally the branches are also equipped with an adjustable inletopening and that is combined with a rotary movable distributor cone sothat a sufficient blend quantity is secured in front of each inletopening by the rotation of the distributor cone. Preferably the blendquantity will be adjusted accordingly. At interconnected buffer/storagecontainer the outpouring blend quantity can easily be adjusted to thedemand via an adjustable discharge sluice. That means, the dischargequantity out of the buffer/storage container will be changed byadjustment of the discharge sluice in case the blend quantity deviatesfrom the target quantity in from of the inlet openings.

The adjustability of the inlet openings acts like the adjustment of theabove described switch. For adjustment of the inlet opening the sameaids like for the switch can be used.

Optionally the distributor cone is equipped with a rotating scraperwhich moves the blend quantity totally or partly successively to thedifferent inlet openings. On the way the inlet openings are suppliedwith the blend in intervals. In dependency of the length and thefrequency of the intervals the blend can flow into the inlet openings.Thereby the length and the frequency of the intervals can be used ascontrol variable.

Optionally a rotating distributor plate is used instead of thedistributor cone. With the distributor plate the same can be achieved aswith the distributor cone.

Optionally also a rotary valve can be used for the supply of thedifferent branches to the production lines.

The FR-A-2564374 shows the use of an auxiliary extruder besides a mainextruder. The auxiliary extruder has the task to feed recyclate into themain extruder. Here the expert knows that recyclate is always onlyadmissible in small percentages referring to the quantity of freshplastic in the main extruder. By means of the auxiliary extruder you candose very well the allowance. A separate melting of the plastic forwood-plastic blends for the solutions of wear problems in the planetaryroller extruder is not shown with it.

Also the EP1262294A1 offers no method of solution for wear problems. Thebrochure describes the production of foam made of wood-plastic blends.

Therefore, due to the above mentioned brochure, it has not been obviousto consult the therein mentioned separate melting of plastic with regardto the solution of the wear problem in planetary roller extruders.

Preferably, the plastic with the additives will be fed into a blend andwill be melted and the melt blend will be homogenized. Then the blendingwith wood is following.

Due to the homogenizing the plastic is distributed evenly onto the woodparticles.

For the above process it is favourable, if the melt is low-viscosity.Every thermoplastic plastic has a melting point and above the meltingpoint a point in which the plastic is gaseous und/or enters into achemical reaction. The point at which the plastic merges into a gaseouscondition is depending of the ambient pressure. Thus, the meltingtemperature can be, depending on the condition of the plastic, e.g. forpolyethylene (PE) between 100 and 135 degree Celsius (PE-LD 105-118degree, PE-MD 120-125 degree, PE-HD 126-130 degree, PE-UHMW 10-135degree, PE-LLD 126 degree). Under corresponding pressure, the melttemperature can be very much higher (PE-LD 160-260 degree, PE-HD 260-300degree, PE-HD-UHMW 240-300 degree).

By pressing of the wood particles their cavities will be considerablyreduced.

Preferably the cavities/pores in the wood will be reduced min. by 10%,preferable by min. 20% of their original volume. Optionally the woodparticles are still further compacted, e.g. reduced to at least 40% oftheir original volume. This happens by compaction of the wood particlesand plant particles respectively. The compaction is scheduled at leastat the surface. The compaction at the surface reduces the consumption ofplastic which is necessary to create a sufficient compound between theparticles and to reduce the moisture absorption and the swelling of theparticles to an admissible degree for the respective application.

A similar effect has the observation of appropriate particle sizes.

Preferably chips are used with a particle size smaller 1 mm, stillfurther preferred smaller or equal 0.8 mm. The used chips do not have aparticle size range. Preferably the main quantity of the chips have aparticle size of 0.3 to 0.4 mm. Main quantity means at least 50%,preferably min. 60% of the chips.

The compacting of wood for the production of blends of weed and plasticitself is already subject of an older proposal. In the older proposal itis intended to pelletize the wood particles before the blending with theplastic. The use of pellets mainly serves for the increase of the woodproportion in the blend, for example to a proportion of more than 80wght % in the blend. Thereby, the pellets facilitate the feeding of thewood particle into the extruder. the pellets namely are running easilyinto the feed hopper of the extruder. Moreover, pellets can be dosedeasily. In practice, however, the pellets did not prove their worth, asthere is the danger that the pellets will not solubilise enough, butdecompose later when they will be wetted after profiling of the blend.The danger is by far higher when using the material in the outdoor areawhen the blend when passing again and again the change of freeze/thaw.

At the pelletizing also a pressing of the wood and a reduction of thecavity of the wood takes place, however, this takes place before thecontact with the plastic melt.

Whereas the wood/plastic blend at the procedure according to theinvention shows surprisingly good resistance values against freeze/thawas well as a much lower swelling behaviour, the contrary occurs whenusing pellets which have been produced before contact with the melt.

As per the invention the processing takes place different from the olderproposal without the great pellets and their necessary comminution, butby use of smaller particles in the above limits, which make acomminution dispensable and become still smaller due to the compactingin the extruder respectively. With regard to pellets there is the dangerthat the pellets will not be comminuted totally and the not comminutedresidues get into the product without the plastic attaining between thejointly grouted particles. Then a moisture absorption of the pelletleads to a swelling and to a loss of the particle bond in the pelletresidue.

The blending of plastic melt and wood occurs according to the inventionunder pre-heating of the wood, so that the flowability of the melt willnot be essentially reduces by the transfer of heat onto the wood.

The merging (blending) of wood and plastic melt occurs preferably in aplanetary roller extruder and in a planetary roller section of anextruder respectively. The planetary roller extruders and planetaryroller sections respectively consist of a centrical central spindle,rotating planetary spindles and an internally toothed housing. Theplanetary spindles and the central spindle also have a toothing. Duringrotation the toothing of the planetary spindles rotate simultaneouslywith the toothing of the central spindle and the toothing of thehousing.

Thereby the wood particles arriving between the teeth of the planetaryspindles will be blended very deeply with the plastic melt andsimultaneously pressed.

In principle the pre-heating of the wood particles can only occur in theextruder. Favourable will be a pre-heating of the wood particle beforetheir feeding into the extruder, because conventional devices for thepre-heating only cause a fractional amount of the costs of an extruder.

Preferably the outlet temperature of the blend out of the extruder ischosen in that way, that the coming out profile strand has a sufficientrigidity in order to cool for example on a roller conveyor with rollsarranged closely together without causing disadvantageous deformations.But also higher outlet temperatures can be handled in that way thatdirectly behind the extrusion die a calibration is scheduled. Withregard to the dimensions of its opening the calibration corresponds tothe required cross section of the extrusion strand. The contact areas ofthe calibration with the extrusion strand, however, are cooled, so thatthe extrusion strand hardens at the outer border and thus becomingstability to pass the roller conveyor.

The calibration is very similar to the extrusion die. The extrusion dieas well has an opening with a cross section corresponding to the crosssection of the desired extrusion strand. The die as well preferably hasa cooling. As far as this cooling is sufficient to stabilize the comingout extrusion strand for the roller conveyor, a calibration in the abovesense will not be necessary. However, the use of a calibration can bemore economically than an extrusion die in special design withespecially long cooling section.

Advantageously, especially the extruded profiles at which the woodparticles have been blended immediately after entry into the planetaryroller section of the extruder with the plastic melt and then have beencompacted between the parts of the planetary roller extruder section,have special high stability and an especially high resistance againstmoisture absorption and an especially high resistance against change offreeze/thaw.

The invention is defined that the melt at the procedure according to theinvention is at least partially penetrated into the cavities/pores ofthe wood before the compaction takes place. In this case the compactionleads at the procedure according to the invention to a furtherfilling-out and to a sealing of the cavities/pores. At the knownprocedure the compaction of the wood leads only to a narrowing of thecavities/pores so that the viscous melt can no longer or only hardlypenetrate into the cavities, however, water and especially vapour can dothis. The penetrating moisture is the reason for the swelling. At achange of freeze/thaw the blend has to bear extreme stress. There is thedanger that the blend will be broken open due to ice formation andmelting of the ice respectively.

Several criteria of the procedure according to the invention are known,however, not in the combination according to the invention.

In this sense the production of blends as per EP 1297933A1 is known asper which at first the plastic will be melted and then blended with woodparticles and kneaded. Afterwards the blend shall be supplied to anextruder and pressed to a sheet. Here a typical production of woodchipboards is concerned. At the production of wood chipboards it isnecessary to wet the wood particles with adhesive and then to pressthem. An extrusion of the chips does not occur at the production of woodchipboards. It is typically to stir the chips with the adhesive in akneader.

At the procedure according to the invention an extrusion is intended.Thereby no additional kneader will become necessary. Wood and plasticare directly supplied into the extruder. The wood/plastic blend iscoming out of the extruder as an “endless” strand. Furthermore, you havenot only to consider more effort at the known procedure, the kneading ofthe liquid melt also leads to a higher plastic proportion.

The EP 1262293A1 contains also a proposal for the blending of wood chipsand plastic. The chips shall have a width of 0.5 to 20 mm, a thicknessof 0.5 to 2.5 mm and a length of 1 to 500 mm. For wetting of the woodchips a jet of liquid plastic will be created, the wood chips areinterspersed into the jet and on a ribbon arranged below a materiallayer is generated which afterwards will be pressed. The extruder doesnot come into contact with the wood chips. The extruder is only intendedfor liquefaction of the plastic. The known proposal does not exceed thebefore defined known proposal. This is also valid as far as in theproposal the wetting of fibers with plastic is mentioned.

The U.S. Pat. No. 5,653,534 shows a procedure for reinforcement ofplastic with fibers. The plastic is brought into melted condition. Thenthe fibers are fed. The emerging product has essentially the sameappearance as plastic without reinforcing inlay. By the procedureaccording to the invention, however, a wood substitute with theimpression of a wood surface shall be created.

Moreover, the processing of a wood/plastic blend with a wood proportionof 60% and more makes incomparable high demands contrary to theprocessing of a fiber/plastic blend with a fiber proportion of 30%.

At the blend according to the invention of wood with the liquid meltbefore pressing/compaction the temperature of the blend proportions isof considerable importance. Favourable is a high temperature of themelt. The higher the melt temperature, the higher the flowability of themelt and the better can the melt penetrate into the cavities/pores ofthe wood before compaction of the wood. The max. melt temperature isdepending on the material. With regard to the melt temperature,preferably a safety distance is kept from the temperature at which themelt passes into a gaseous condition or a chemical reaction occurs. Thesafety distance amounts optionally to min. 5%, still further preferredmin. 10% and highly preferred min. 15% from the temperature, at which apassing into the gaseous condition or a chemical reaction occurs.

Moreover, the melt temperature is restricted due to the condition of thewood.

Depending on the condition the wood tends at higher temperature to anundesired discoloring.

There are resulting different processing temperatures for the melt,depending on material and pressure. Whether the processing range can beexhausted completely or partially is depending on the used wood and onthe temperature of the wood. At higher temperatures a highly liquidplastic is arising. That means, the plasticization according to theinvention contains an intense liquefaction.

Preferably plastic is used which has been max. once recycled. Theoftener the material has been recycled the worse the flowability of someplastics will become. Or a plastic is used consisting of a blend offresh material with recycled material and which has as least the sameflowability as a material which has been recycled in totally not morethan one time.

Still much more preferred is the use of an overall fresh plastic,non-recycled material.

Optionally the plastic will be plasticised together with the additivesor the additives will be blended with the plastic after theplasticization of the plastic before the blending with the woodparticles will take place. To these additives belong preferablydyestuffs and bonding agents as well as water repellents.

Wood particles are preferably used in the form of chips, e.g. in theform of wood shavings. Wood shavings accrue in large quantities at theprocessing of wood. Simultaneously the dimensions of wood shavings arewithin certain limits. Usually, wood shavings are conveyed by means ofpressurized air. By means of the pressurized air the wood particles canbe transported within wide limits to any place, e.g. to the feed hopper.Usually, pressurized air accrues by use of blowers which are sucking inthe air at the one side and are pressing the air at the other side intoa transmission pipeline. At the goal of the wood particle transport thepressurized air must be separated again from the wood particles. This isdone by means of suitable filters. In practice, however, the filterscannot separated every dust particle from the pressurise air. Fine dustarrives in a more or less large amount into the surroundings.

In the further formation of the invention the outlet of the fine dustshall be reduced. Therefore suction air is preferably used for thetransportation of the wood particles. At the goal of the suction airtransport the wood particles are separated from the suction air by meansof filters, as done at the pressurized air transport.

Optionally the wood is used in pre-heated condition. The pre-heated woodbrings forward the penetration of the melt into the cavities/pores,because when contacting the wood the melt gives off heat only in asmaller range than at room temperature of the wood. Furthermore thepre-heating of the wood can cause a drying.

The plasticization can take place in different devices. Imaginable is abatch-wise liquefaction. For the liquefaction of the plastic a heatedpressure vessel is scheduled. When using one single pressure vessel withone single chamber the batch-wise operation allows only one intermittentliquefaction process. With two vessels, however, a continuousliquefaction process can already be brought out. The same applies forone single vessel with two melt chambers, which can be alternately fedand depleted. The depletion of the vessel is preferably executed bymeans of a pump. The pump does not only care for a quick depletion, thepump can also build up a high pressure in the melt.

Preferably the plasticization of the melt is executed in an extruder. Inan extruder the melt temperature can easily be controlled.

As far as a pre-heating of the wood is required, the wood will be heatedat the same time at another place. After the heating the wood particlesare blended with the plastic, the above described homogenizing andcompaction takes place.

The heating of the wood particles can occur single-stage or multistage.The heating occurs before the contact with the plastic. Depending on thetemperature of the supplied melt and on the further processing of themelt and the therewith connected temperature control the wood canreceive a further heating or a cooling by the supplied melt and thefurther processing.

The pre-heating of the wood amounts preferably to min. 50 degreeCelsius, still more preferred mind. 100 degree Celsius and highlypreferred mind. 150 degree Celsius.

Optionally the multi-stage pre-heating of the wood will be effected bydifferent heating equipments. Each heating device can work continuouslyor discontinuously. A continuously working heating device is for examplea heating band and/or tunnel furnace.

The heating band is a heated belt conveyor at which the wood particlesare heated. The heating band can also conduct the wood particles undersuitable heat radiators. Thereby it is favourable to house the heatingband in order to avoid a loss in temperature.

A tunnel furnace has a housing. A tunnel furnace differs from theheating band that not the conveyor belt, but the housing is equippedwith a heating device and/or that a heating gas is led through thehousing. The heating temperature is chosen in that way that any dangerof combustion/fire danger for the wood will be avoided.

A discontinuous heating can occur in a container until the woodparticles have reached the requested temperature. Optionally thecontainer a gaseous heating medium is passed through the container.Opportune are inert heating gases. Inert heating gases can be ledthrough the containers with a far higher temperature as e.g. air withoutthe risk of fire danger.

After the requested heating of the wood particles the container can beopened and the wood particles can be discharged out of the container forthe blending with the plastic.

When the pre-heating takes place totally or partially in an extruder andan extruder section (module) respectively then the blending of plasticand wood is executed preferably in a downstream further extruder ordownstream extruder section. Each extruder/extruder section is equippedwith a material feed opening and with an outlet for the compoundedmaterial. The material feed opening is located at the end of theextruder. From there the material will be supplied with the requestedtreatment to the material outlet at the other end of the extruder.

Preferably the wood particles are supplied into the feed opening of theextruder in which the blending with the plastic is intended. The plasticwill be plasticised preferably in a separate extruder and injected asmelt into that extruder, destined for the blend, as soon as a sufficientpressure build-up in the supplied wood has happened. At simultaneous useof the extruder for the heating of the wood the injection place will bechosen in that way that the heating section will be long enough in orderto achieve the requested temperature.

The extruders are known in several types of construction.

There are single-screw extruders, twin-screw extruders and planetaryroller extruders.

The single-screw extruder has only one screw surrounded by a housing.The twin-screw extruder has two parallel side-by-side arranged screwswhich are rotating together. The screw can rotate in the same directionor can rotate in opposite directions. The single-screw extruder as wellas the twin-screw extruder normally has multipart screws. Thereby amultitude of bushes are arranged in series in axial direction. Thebushes have a toothing outside and inside a through-hole so that theycan be tensed up against each other with a tensioning bolt. This kind ofconstruction allows to design the twin-screw extruder via a requesteddistance as kneader.

The planetary roller extruder has an axially arranged central spindlewhich will be driven. Around the central spindle there are arrangedplanetary spindles. The planetary spindles rotate with the centralspindle.

The planetary spindles are surrounded by an inner toothed housing.

The planetary spindles rotate with the internal toothing of thehousings.

Every rotation of the central spindle effects a rotation of theplanetary spindles. Thereby the planetary spindles rotate like planetsaround the central spindle.

The different types of construction can also appear in combinations.E.g. the primary extruder of a tandem line can be composed of asingle-screw extruder or twin-screw extruder whereas the secondaryextruder is a planetary roller extruder. The primary extruder and thesecondary extruder can be driven with different speed. This offersconsiderable advantages.

The combination of different extruder systems can also take place in onesingle extruder. Thereby the extruder systems, combined with each other,form extruder section in the extruder. As already mentioned at anotherplace the extruders can have different tasks and several tasks can befulfilled successively in the extruder. These tasks can be named asprocess steps. On the other hand extruders can consist of sections dueto constructive reasons. The constructive extruder section cancorrespond with the process steps of the extruder, but it is notnecessary.

As per the invention the plastic will be liquefied before it will beblendes with the wood. The liquefaction occurs in a separate extruder.At the same time this can be used for the processing of the plastic.Thereby one speaks of the reprocessing of the plastic and the followingprocess steps can occur for example: feed in of the plastic, melting ofthe plastic, dispersion of additives in the melt and homogenization ofthe generated melt.

At separate recycling of the plastics in a separate extruder the processsections are for example feeding of the plastic, melting,homogenising/dispersion of the separate melt.

At the processing of wood/wood particles in an extruder the processsections are e.g. the feeding, injection of the melt, blending with themelt, homogenising of the blend, degassing and cooling of the blend toextrusion temperature.

The before mentioned processing steps of the wood/wood particles canalso take place in two or several downstream arranged extruders. At twodownstream arranged extruders you speak about a tandem line with oneprimary extruder and one secondary extruder. At several downstreamarranged extruders you speak about a cascade line.

The tandem line and the cascade line are outstandingly suitable for thedegassing of the blend. Thereby the blend can fall out of the dischargeend of the primary extruder into the below arranged feed opening of thesecondary extruder.

Between the primary extruder and the secondary extruder there can alsobe destined a conveyor, e.g. belt conveyor. When using the conveyor, theblend can fall onto the conveyor and can be conveyed horizontally orinclined downwards or on inclined upwards by means of the conveyor.

On the way from the primary extruder into the secondary extruder thedegassing can take place. The degassing can take place under ambientpressure. In case the degassing shall be enforced this can take place byuse of a vacuum. For this the hauling distance from the primary extruderto the secondary extruder will be surrounded by a housing.

At the tandem line as well as at the cascade line the blend istransferred in a heat into an extrusion product, especially an extrusionprofile. The heat excludes a vast cooling, especially a cooling down toambient temperature. As per the invention the extrusion product withreactive blending components before the reactive blending components canreact. Such blending components can be water repellents.

Moreover, the blend has no solidification of the plastic before theentry into the last extruder of the processing distance (e.g. secondaryextruder of the tandem line). Otherwise the solidified blend particleswould break open in the secondary extruder without securing that thewood of the particles would be secured sufficiently against moistureabsorption at the breaking point.

As far as at the production extruders are used which consist of housingsections/modules, these housings will be fixed together in known mannerby means of flanges, preferably screwed together.

As far as several housing sections/modules are belonging to the extruderwhich are designed as single-screw sections/single-screw modules (like asingle-screw extruder) and which are arranged downstream, then there isintended a joint screw for the different single-screwsections/single-screw modules. Joint means the screw continues from onesingle-screw section/single-screw module in the next module. That is ausual technique.

If moreover a planetary roller extruder section/planetary rollerextruder module attaches at a single-screw extruder section/single-screwmodule so it is usual that their screw will continue as central spindlein the planetary roller extruder section/planetary roller extrudermodule. Such a situation occurs for example in case one or severalsingle-screw extruder sections/single-screw modules are intended for theprocess step “compounding of the plastic” and in case a planetary rollerextruder section/planetary roller extruder module is intended for therange “cooling of the melt to extrusion temperature”.

The use of a collective screw for different extruder sections isrelatively easy at modern extruders. These screws will be assembled outof bushes which will be penetrated by a collective rod and will betensioned with each other. This kind of construction also has otheradvantages.

Often the extruder sections are formed also in the extruder housing.

Thereby the housing sections will be tensioned with flanges at the ends.

In the following it is only spoken about extruders. This includes thecombination with same or other extruders as well as the combination insections of different extruder systems in one extruder. Furthermore, thecombination of extruder sections of the same system is included as well.

All modern extruders are equipped with a heating-cooling device.

For this the extruders are equipped internally with a liner. The linehas outside channels which are incorporated into the outer area of theliner like grooves or threads or screw flights. The outside arrangedchannels can relatively easy by cut by turning and milling.

The thus treated channels are inserted into the internally smoothborings of the housing. Through the channels are pressed cooling mediumsor heating mediums optionally in direction of the melt flow or contraryto the direction of the melt flow. Optionally any heating or coolingdistances can be created. Due to the coiling of the channels the heatingor cooling medium is led controlled for a long time along the wall ofthe housing and the outer wall of the liner respectively. this securesan extreme cooling or heating.

Whether a heating distance or a cooling distance is concerned isresulting from the respective procedure. Thereby, heat must be added orabstracted from the passing through medium.

Theoretically the channels could also be arranged at the internal areaof the housing and the outside of the liners could be smooth.

The incorporation of the channels at the internal side of the housing ismuch more laborious than the before described incorporation into theoutside of the liner.

Moreover, it is of advantage to assemble the liners by shrinkage in theextruder housing. This happens by heating of the extruder housing. Dueto the heating the extruder housing is enlarged. During this conditionthe cold liner will be slid into the bearing bore of the extruderhousing. During the following cooling down the extruder housing iscontracted and surrounds the liner closely if the liner has acorresponding external dimension and the boring of the housing has acorresponding inside dimension. Such a situation occurs when using a socalled interference fit. At the interference fit the liner has outsideat least exactly the same diameter or an insignificant larger diameteras the extruder housing inside.

The known interference fits are designed in that way that after theshrinkage a separation of the liner from the extruder housing will bepossible by means of heating of the housing without any damage of theparts. The separation is important in order to rework, if necessary, thetoothing of the liner or to exchange the old liner against a new one.

For the compounding according to the invention of a plastic/wood blendthere is preferably scheduled one extruder consisting of differentsections of different kind of construction, namely preferably of onesingle-screw module/section and one or several other planetary rollermodules.

Thereby it is of advantage when the single-screw module is designed insuch a length and heated that the filled-in wood has reached therequested temperature when leaving the single-screw module.Advantageously the single-screw module simultaneously causes a pressurebuild-up in the wood, which avoids an escape of the injected plasticmelt in direction of the feed opening for the wood.

It is also of advantage when the plasticised plastic between thesingle-screw module and the further for the blend of plastic and woodscheduled extruder modules is supplied via a stop ring or via anintermediate ring.

To each module and section respectively belongs a surrounding, normallytubular housing. This is valid for modules and sections respectively ofevery kind of construction. The houses are in any case at each endequipped with a collar (flange). At this collar the fastening takesplace with the housings of neighbouring modules and section respectivelyand if necessary with the housing of the gear normally scheduled for anextruder. The gear belongs to the drive of the extruder.

Between two housings an intermediate ring can be of advantage.

The intermediate ring can fulfill different tasks. It can fulfillindividual tasks or several tasks at the same time.

The tasks are for example

-   a) the centring of the correspondent ends of the housings and/or-   b) the insert of process agents and/or-   c) the measurement of process parameters and/or-   d) the degassing and/or-   e) the elongation of the planetary roller part

The elongation can occur thereby that the housings will only be spaced.

Thereby the intermediate ring can have different forms. In one form theintermediate ring forms a distance piece which is located between theends of the housing. In another form the intermediate ring has the formof a bush.

Thereby the intermediate ring can encircle the central spindle in adistance. In case the housing of the corresponding planetary rollerparts has conventional stop rings then a cavity occurs between thecentral spindle and the intermediate ring.

Optionally the cavity is chosen in such a size that the planetaryspindles can extend through the cavity and can rotate in the cavity.

Optionally, the intermediate ring has also inside the same toothing likethe housings of the planetary roller part. Then the planetary spindlesextending through the cavity of the intermediate ring can rotate at thesame time with the internal toothing of the intermediate ring.

Due to the elongation of the planetary roller parts unusual lengths canoccur.

According to the invention also planetary spindles with conventionallengths can be used. This occurs thereby that the planetary spindles arealigned lengthwise and then arranged to one another. The planetaryspindles can in that position rotate without problems around the centralspindle. They are kept in the position by the tooth depth with thecentral spindle and by the tooth depth with the inner toothed housing.

That means that the spindles, lengthwise aligned and arranged to oneanother, conduct themselves like one single oversized planetary spindle.

As far as the planetary spindles, jointly forming an oversized planetaryspindle, do not form a suitable length, preferably one of the respectiveplanetary spindles will be cut to a suitable length. It is of advantagewhen this takes place before the heat treatment of the planetaryspindles by which the planetary spindles can be made wear-resistant.

The planetary spindles can be treated easier with conventional aidsbefore the hardening or heat treatment of the surface of the planetaryspindles.

By the assembly of the planetary spindles according to the invention therisks of an arising warpage, occurring normally due to a heat treatment,will be minimized. The warpage occurring at a heat treatment, isdepending on the length. Depending on the form and the material of theplanetary spindles more or less warpage can occur.

Optionally the parts, destined for an oversized planetary spindle, canbe connected at the front surfaces at which they contact each other.Thereby can the one part with a journal seize into an opening of theother part.

The intermediate ring, intended for the supply of the liquid plasticmelt, can have different forms.

A pipe section can be concerned which is, except its minor axial length,comparable to the housing of the single-screw module and sectionrespectively. It also has at the ends collars by means of which thefastening of the intermediate ring at the housings of the neighbouringextruder modules and sections respectively is executed.

The intermediate ring is penetrated by the extruder screw/spindle. Inthe range of the single-screw module and single-screw sectionrespectively, the extruder screw/spindle is a single-screw, in the rangeof planetary roller modules a central spindle.

Normally the extruder screw/spindle is designed in several parts. Allparts have a bush form with a toothing at the outside. The centre holeis penetrated by an anchor which has the task to tension all bushes witheach other.

In the single-screw module the extruder screw/spindle is composed of amultitude of parts/bushes having a different toothing at the outside inorder to exert influence by means of the design of the screw flights onthe compacting and treatment respectively of the feedstock in thesingle-screw module.

In the planetary roller module normally there is intended a single-piecebush forming the central spindle and which is kept with the same anchorwhich keeps the bushes of the single-screw module.

The anchor is running also through the above describes intermediate ringfor the injection. In the intermediate ring there is also intended abush on the anchor. The bush can have outside the same or anothertoothing like the single-screw at its end.

Optionally the intermediate ring is equipped in the same way like theextruder modules/sections with a heating-cooling device which, accordingto requirements, allows a cooling or a heating.

The intermediate ring can also be assembled without collar. Then theintermediate ring is inserted between the collars of the neighbouringhouses, i.e. between the housing of the single-screw module and thehousing of the planetary roller module. Afterwards, the two respectivecollars are tensioned against each other by means of tensioning screwsor other tensioning means.

It is favourable when an intermediate ring gears into a centring openingof the neighbouring housings and collars respectively or vice versa theneighbouring houses gear into a centring opening of the intermediatering. A centring opening can be made by a hollow at the front area ofthe intermediate ring and the neighbouring housings respectively.Thereby a small hollow may be sufficient. A corresponding nose at theopposing front area corresponds to the hollow.

For the supply of the liquid melt there are scheduled in theintermediate ring preferably several inlet borings which are evenlydistributed on the circumference. Several cables may go to the differentinlet borings. But there can also be a connection of the inlet boring bya circular groove in the intermediate ring which is closed by means ofthe cover and which is fed with liquid melt via a joint supply line.

The supply lines connect the extruder, intended for the liquefaction ofthe plastic, with the intermediate ring. It is advantageously to isolateand to heat the supply lines so that no unwanted decrease of temperaturein the melt occurs or the melt even freezes.

Optionally there are scheduled valves or gates for adjustment of themelt flow in the different supply lines to the intermediate ring. Thevalves allow optionally an adjustment and influence on the melt flowduring operation. This can be used for a smoothing out for the creationof differences. Additionally or instead of the valves an alteration ofthe melt flow can be reached by inserts which will be located in thesupply lines. The inserts can also be scheduled in the intermediatering.

Incidentally, the melt flow is determined by the speed of the extruderwhich is intended for the plasticization of the plastic.

Optionally the liquid melt can also fed into the single-screwmodule/section at the end of the heating distance. Then the extruder,destined for the creation of the liquid melt, is connected directly tothe single-screw module/section, intended for the heating of the wood.

The connection is optionally executed thereby that the extruder,destined for the liquefaction, is flanged directly to the housing of thesingle-screw module/section, or e supply line is intended which leads tothe housing of the single-screw module/section.

The extruder directly flanged to the single-screw module and whichserved for the production of liquid melt can also be described as sidearm extruder. This extruder can be of the same kind of construction likethe single-screw module, but also an extruder of a different kind ofconstruction can be used.

The housing of the single-screw module/section must be bored through forthe supply of the liquid melt. The double-walled housing shell,necessary for the heating-cooling, will be bored through for this. Inorder to avoid on the one hand the flowing of the melt into the hollowshell and the heating-cooling medium on the other hand does not pollutesthe melt there can be mounted a flange which extends with a collar intothe boring and thus closes the hollow shell again.

For the supply of the liquid melt also the neighbouring planetary rollermodule can be tapped. Also there is a housing twin-shell, which will beopened by the boring and must be closed again.

As per the DE 10356423 this will be reached by means of a liner thereby,that

-   -   the boring is fed through the housing and is extended into the        liner which is located in the liner,    -   whereas the material supply with a supply housing extends into        the boring and    -   aa) whereas the boring shows a circular expansion in the range        of the channels serving for the heating-cooling, so that around        the supply housing there occurs a circular connection channel        for the channels serving for the heating-cooling    -   or    -   bb) whereas the boring extends into a groove which reaches over        the whole circumference or over a part of the circumference of        the liner being located in the housing and the width of which is        larger than the diameter of the supply housing so that around        the supply housing a connection channel occurs for the channels        serving for the heating-cooling    -   or    -   cc) whereas a supply housing is used which extends into the        liner, whereas the supply housing is equipped in the range of        the channels serving for the heating-cooling with at least one        connection channel for these channels.

Advantageously the connection channel as per cc) can be incorporatedoutside into the supply housing by cutting and milling.

Preferably there is intended a supply housing with several connectionchannels so that any interruption of a channel, occurred by the boring,is abolished or bridged by a connection channel.

Much more preferred is a supply housing with several connection channelslying upon another. The single connection channels can be incorporatedinto the supply housing as adjoining grooves. The channels can lieoutside at the supply housing.

Thereby it is of advantage when the connection channels lying uponanother have a height which is smaller than the width. At the same timethe width has been chosen in such a dimension that the connectionchannels have a sufficient diameter for an undisturbed transfer of theheating-cooling medium, preferably the diameter is equal. It will be ofadvantage when the height of the connection channels is chosen in thatway that the total height of the connection channels, lying upon anotherand being separated from each other by a land, is not higher than theheight and depth respectively of the channels in the liner serving forthe heating-cooling. The channels for the heating-cooling medium must bediverted and sealed in the passage of the material supply in order toavoid a leakage of the heating-cooling medium. By redirection there canoccur channels lying upon another as per proposal DE10356423.Furthermore, the sealing takes place by a tube shell of the housing forthe material supply (feed housing). The exterior tube shell in thenequipped with inlet openings and outlet openings. Each inlet opening isarranged in that way that it is lying at the respective end of thechannel occurred by the described interruption. Optionally theconnection channels have been incorporated also at the inner side of thesupply housing and the connection channels are closed by an inner lyingtube shell. Due to the inlet openings and outlet opening incorporatedoutside into the supply housing there occur also connection channels.

-   -   or    -   dd) whereas the boring is enlarged opposite the supply housing        and whereas there is intended in the housing an insert with an        opening or a connection for the support of the supply housing.        The insert has outside or inside one or several connection        channels which will be designed or fabricated respectively like        the connection channels under cc).    -   ee) whereas there is an insert in the boring at which the supply        housing is fixed and the insert is equipped outside or inside        with one or several connection channels which are designed or        fabricated respectively like the connection channel under cc).

The above described supply housing can extend the liner, located in theextruder housing, so far that it will end totally or partially with theinner surface of the liner. Is the supply housing adjusted to the innersurface of the liner, it can end totally with the inner surface of theliner. This can also be applied to inter toothed liners of an extruderhousing. The adjustment by cutting or milling or grinding or by theadjustment to inner toothed housing liners will be achieved thereby thata toothing will be incorporating into the housing wall in the same waylike the internal toothing of the liner being situated in the extruderhousing. Opportune is thereby the use of the spark-erosion for thetoothing.

For the melting of plastic according to the invention before the mergingwith the wood particles also a planetary roller extruder module can beused instead of a single-screw module.

Each of these extruders has a housing which can form the above describeshousing for the material supply (feed housing).

The side arm extruder can have several types of construction.

There are single-screw extruders, twin-screw extruders and planetaryroller extruders.

The single-screw extruder is the cheapest construction of an extruder,but also the extruder with the smallest construction method.

When using a single-screw extruder the inclination of the screw shallcause the requested conveying effect.

The twin-screw extruder has two parallel arranged screws rotating witheach other. The twin-screw extruder is indeed more complex than thesingle-screw extruder. The twin-screw extruder, however, has a by farhigher conveying effect than a single-screw extruder. Nevertheless thetwin-screw extruder is still relatively favourable. Moreover, thedimensions of the twin-screw extruder are still very small. When usingthe twin-screw extruder it can be easily ensured that the liquid meltwill be injected with the correct pressure into the planetary rollermodule, due to the high conveying effect.

Optionally, a planetary roller part is used for this side arm extruder.During operation also this planetary roller part can be operated in thatway that the necessary pressure for the injection of the liquid meltoccurs.

The drawing shows different examples of design of the invention.

FIG. 1 shows FIG. 1 shows an extruder for the production of blends ofplastic and wood particles. The extruder has four sections. The extrudersections are designed as planetary roller extruder sections, the fourthextruder section is designed as single-screw extruder and serves for thematerial feed.

Thereby the housings of the planetary roller extruder sections aremarked with 5 and the housing of the single-screw extruder section ismarked with 1. Each housing 5 has welded flanges 6 and 7, which arescrewed to each other in not demonstrated form. The housing 1 isequipped with flanges 3 and 4 which serve as fastening like the flanges6 and 7.

Each housing 1 and 5 is internally lined with liners.

Furthermore, at the inner side of the housing are shown channels whichcan be charged with heating agents or cooling agents if necessary.

The shown ends of the housings 5 are equipped with a clearance for acentring ring 111 and stop ring and wear ring 8.

The stop ring and wear ring 8 form the slide face for the planetaryspindles 10. The stop ring and wear ring 8 have an internal diameterbeing smaller than the marked rolling radius of the planetary spindles10.

All extruder sections have a joint spindle. This joint spindle is markedwith 9 in the range of the planetary roller extruder sections and ismarked with 19 in the range of the single-screw extruder sections whichserve as feeder.

In the design example the feedstock is formed by wood chips. The woodchips are dosed via a hopper through an opening 2. The wood chips aredrawn off in not demonstrated form out of a silo by means of a vacuumconveyor tube and led to a filter arranged above the hopper andseparated from the suction air. By means of a not demonstrated stuffingscrew the wood chips are drawn off out of the filter into the hopper. Inthe hopper there takes place a volumetric measurement of the quantity ofthe wood chips. In other design examples there is intended an additionalgravimetric measurement or only a gravimetric measurement. The vacuumconveyor tube is controlled by means of the measurement results.

The first extruder section forms a feeder for the second extrudersection. In the second extruder section there takes place the dosing andblending with liquid plastic melt and a compacting; in the thirdextruder section there takes place a homogenization of the blend. In thelast extruder section there takes place a cooling-down of the blend tooutlet temperature. In the design example the wood has a proportion of70 wght % and the plastic a proportion of 30 wght % of the blend. Inother design examples the wood proportion amount e.g. to 65% or 75% ofthe blend. Thereby the charges like colour and water repellents arecalculative added to the plastic proportion.

The thus composed blend enters at the extruder tip 12 into a notdemonstrated extrusion die the opening of which is replicated to afloorboard so that due to the extrusion of the blend an endless strandwith the cross section of a floorboard is created. Floorboards with theappearance of a timber floor board are arising from the not demonstratedcutting of length of the extrusion strand.

The floorboards are profiled at the bottom side. The profiles are chosenin that way that there is a wall thickness of 10 mm. In other designexamples a wall thickness of 8 to 12 mm has been chosen.

The profiling includes a cavity formation and chamber formationrespectively.

In FIG. 2 there is intended a side arm extruder 20 at the planetaryroller part 5 for the feed of the liquid melt.

The side arm extruder is designed as twin-screw extruder. The twin-screwextruder consists of two counter-rotating screws. In the side armextruder 20 are in not demonstrated form plastic pellets, in the designexample polyethylene (PE) pellets, filled in, compressed and heated sothat liquid melt is generated from the pellets. Together with the PEpellets additives like colour and water repellents are added at the sametime. In the melt the additives are distributed advantageously.

By means of the twin-screw extruder the liquid melt can be injected withconsiderable pressure into the planetary roller part 5. The liquid meltwets the wood particles at the surface and penetrated into thecavities/pores. During the following compacting of the wood particlesthe cavities/pores are reduced and closed by the melt, which stillremained open during the injection of the melt. The melt is supplied atsuch a temperature at which the melt remains still liquid even it hadreleased heat when contacting the wood particles.

Between the different wood particles the melt takes effect like anadhesive.

The housing of the side arm extruder 20 is multipart. The header 21 assupply housing is located in a boring of the housing of the planetaryroller part 5. The boring extends at the same time the respective liner22 and ends with the inner surface of the liner 22.

In the design example the side arm extruder is suited for the creationof very high feed pressures.

In the design example of FIG. 1 the planetary roller part 5 shown inFIG. 4 is used directly after the material feed and directly after thefeed part respectively. In another design example the planetary rollerpart 5 with the side arm extruder is used after the second planetaryroller part as third planetary roller part.

In further design examples every planetary roller part can be equippedwith a side arm extruder for the supply of liquid melt.

In a further design example as per FIG. 3 the extruder housing marked 30of the side arm extruder comes up to the housing 30 of the planetaryroller part 5. The extruder housing 30 is connected with an insert 31which is located in a boring of the housing 5. The insert 31 has at itsoutside two grooves 32 and 34 lying upon another. Between the twogrooves 32 and 34 there is a land 33. These grooves form connectionchannels. Two connection channels are intended because the housing islined with a liner 22 and because the liner 22 is equipped inside andoutside with a toothing. The not demonstrated internal toothing servesfor rotating with the rotating planetary spindles which are demonstratedin FIG. 1. The outer toothing of the liner 22 is interrupted at twoplaces for the respective boring for the insert 31. Each connectionchannel is destined for one interruption and connects the oneinterruption end with the other interruption end.

The grooves 32 and 34 are closed by an outside tube shell 35 so that noheating agent or cooling agent can enter or leave wrongly.

In the design example there is demonstrated an inlet opening 37 of thegroove 34. the inlet opening of the groove 32 is located at another, notdemonstrated place.

The outlet opening is located in the design example on the diametricalopposite side of the insert 31 which is not demonstrated.

The design example as per FIG. 4 shows the use of an extruder for thefoam production. Thereby a liquid blowing agent is pumped into theplastic melt via an insert 40 which is located in the extruder housing5.

In the range of the liner 41 there is intended a not demonstrated insertwhich differs from the insert as per FIG. 3 thereby that only oneconnection channel is intended.

The FIG. 5 to 7 shows a further extruder with a planetary roller modulewith a housing 101 and a flanged side arm extruder.

The planetary roller module has an extruder housing with a linerarranged therein. The housing is shrinked on the liner.

Outside the liner has milled in channels for the heating-cooling agentsfor cooling or heating. The channels are running in form of spirals atthe outside area of the liner and occurred by milling. In the designexample there are intended two different heating-cooling areas. The onearea is marked by inlets and outlets 120, 121, the other area by inletsand outlets 122, 123.

The side arm extruder is a twin-screw extruder and consists of differentpart. Two parallel arranged screws 116 are belonging thereto which arerotating together and are driven via a motor. Between motor and screws116 there a scheduled a gear and a coupling 11 with a housing 115.

Furthermore the side arm extruder is assembled of a feed part 109 and anextrusion part 102. The feed part 109 has an opening for a notdemonstrated material supply.

In the extrusion part 102 the side arm extruder has a heated-cooledhousing.

The housing has a staged end 104 with which it is located in a boring103 which is extending through the housing of the planetary roller part101 and the respective liner to the internal space of the planetaryroller module. In the range of inlets and outlets 122, 123 the boringrequires a special guiding for the channels at the outside of the linerwhich are intended for the heating-cooling agent. There the channels areled around the range of the boring so that also the surrounding of theboring will be heated-cooled.

An additional possibility for the heating-cooling arises in thesurrounding by the heated-cooled front end of the side arm extruder.

The boring goes through the above described stepping to a contact area102 at the housing.

In a further design example the FIG. 8 to 10 show a complete line forthe production of blends of wood particles and plastic.

Thereby an extruder with one feed part 201 and two planetary rollerparts 202 and 203 is used. The feed part 201 has the design of asingle-screw and corresponds in principle to the singe-screw part andfeed part respectively of the FIG. 1. The two planetary roller parts 202and 203 correspond in principle to the planetary roller parts 5 and 10of the FIG. 1.

The feed part 201 is fed with wood chips out of a hopper 205. The woodparticles are drawn in into the feed part and slightly pre-heated.

To the line belongs also a laterally arranged extruder 204. Thelaterally arranged extruder 204 is a single-screw extruder and servesfor the melting of the plastic. The laterally arranged extruder injectsthe liquid melt into the extruder between the feed part 201 and theplanetary roller part 202.

An intermediate ring is intended between the feed part 201 and theplanetary roller part 202. The intermediate ring is demonstrated in FIG.11. In FIG. 11 the housings of the feed part 201 is marked with 211 andthe housing of the planetary roller part 202 is marked with 210. The twoopposite housing ends are equipped with a collar 214 and 213. Betweenthe two collars there is inserted an intermediate ring 212. Theintermediate ring 212 is inserted in eccentric openings at the frontsurface of the collars. The intermediate ring 212 has several openings,evenly spread on the circumference, to which lead melt lines 216 fromthe extruder 204. The intermediate ring 212 is tensioned between thecollars 211 and 213. The pre-tensioning is effected by means oftensioning screws of which only a midline 215 is demonstrated. Thetensioning screws extend both collars and are working together with thescrew nuts.

After the conjuncture of the liquid melt and the wood particles theblending and homogenization and a compacting take place in the planetaryroller part 202. In the subsequent planetary roller part a cooling downto the requested outlet temperature takes place. In the design examplethe temperature of the blend is still so high that the blend isevaporating and loses unwanted moisture on the way.

After the outlet and the evaporation a distribution of the blend toseveral further extruders takes place in the design example. For this adistribution device 220 is scheduled. The distribution device 220 leadsthe blend to the downstream single-screw extruders 221, 222 and 223. Theblend can be supplied evenly or differentially to one or several ofthese single-screw extruders, or to all together. The aim is to extrudeas and when required different or the same profile formats by means ofthe singe-screw extruders 221, 222 and 223.

In the design example the distribution device is created by a switch inthe hauling distance of the blend after having left the extruder. Bymeans of the switch the conveyed quantity of blend can be diverted tospecial singe-screw extruders or can be divided into two or three flowswhich are led then to the respective singe-screw extruders.

1. A method for producing a blend of wood particles and plasticparticles in an extrusion line that includes a feed part (201), a sidearm extruder (204), and at least one planetary roller part (202) thathas a central spindle, multiple planetary spindles, and a surroundinghousing, with the multiple planetary spindles rotating about the centralspindle in the housing as a result of an internal toothing of thehousing, said method comprising the steps of: feeding the wood particlesinto the feed part (201), a majority of the wood particles having a sizeof between 0.3 and 0.4 mm and the wood particles having a maximum sizeof 0.8 mm; feeding the plastic particles into the side arm extruder(204) and then, independently of the wood particles, liquefying theplastic particles into a plastic melt; advancing the wood particles outof the feed part (201) and into the planetary roller part (202);injecting the plastic melt into the planetary roller part (202) with thewood particles, such that the wood particles have a proportion of atleast 60% by weight in the blend; blending and homogenizing the plasticmelt with the wood particles in the planetary roller part (202);compacting the blend in the planetary roller part (202); and dischargingthe blend out of the extrusion line.
 2. The method as recited in claim1, and further comprising the step of adding one or more of thefollowing into the plastic particles prior to blending and homogenizingthe plastic melt with the wood particles: colours, couplers andadhesives, stabilizers, lubricants, or water.
 3. The method as recitedin claim 2, and further comprising the step of pre-heating the woodparticles to a temperature of at least 50 degrees Celsius.
 4. The methodas recited in claim 3, in which the step of pre-heating the woodparticles occurs outside of the extrusion line.
 5. The method as recitedin claim 1, and further comprising the step of compacting the woodparticles, such that a void volume of the wood particles is reduced byat least 10%.
 6. The method as recited in claim 1, wherein the plasticmelt is injected into the planetary roller part (202) and merged withthe wood particles under pressure.
 7. The method as recited in claim 6,wherein, in the step of injecting the plastic melt into the planetaryroller part (202), the plastic material is sprayed against the woodparticles.
 8. The method as recited in claim 1, wherein the plasticparticles are fed continuously into the side arm extruder and liquefied.9. The method as recited in claim 1, wherein the feed part (201) is asingle-screw extruder.
 10. The method as recited in claim 1, wherein thefeed part (201) has a single-screw design, wherein the plastic melt isproduced in the side arm extruder (204), and wherein the plastic melt isfed between the feed part (201) and the planetary roller part (202). 11.The method as recited in claim 1, wherein the extruder line furtherincludes an intermediate ring (212) interposed between the feed part(201) and the planetary roller part (202).
 12. The method as recited inclaim 11, wherein the-intermediate ring (212) is equipped with a collarwith which the intermediate ring (212) is fixed at a neighboring collarof the feed part (201) and at a neighboring collar of the planetaryroller part (202).
 13. The method as recited in claim 11, wherein theintermediate ring (212) seizes into an eccentric opening in aneighbouring front face of the feed part (201) or contrary the planetaryroller part (202), and the feed part (201) seizes into an eccentricopening at a front face of the intermediate ring (212).
 14. The methodas recited in claim 1, and further comprising the step of distributingthe blend downstream to multiple single-screw extruders (221, 222, 223).15. The method as recited in claim 14, wherein the step of distributingthe blend downstream to multiple single-screw extruders (221, 222, 223)makes use of a distributor.
 16. The method as recited in claim 1,wherein the side arm extruder (204) includes a boring extending throughan extruder housing and a liner of the planetary roller part (202) whichis located therein, and wherein a tube extends into the boring, suchthat, between the tube extending into the boring and an inner wall ofthe boring, there is a distance forming a cavity for connecting coolingmedium channels or heating medium channels.
 17. The method as recited inclaim 1, wherein a minimum of 60% of the wood particles have a size of0.30 to 0.40 mm.
 18. The method as recited in claim 1, and furthercomprising the step of pre-heating the wood particles to a temperatureof at least 100 degrees Celsius.
 19. The method as recited in claim 1,and further comprising the step of pre-heating the wood particles to atemperature of at least 150 degrees Celsius.
 20. The method as recitedin claim 1, wherein the plastic particles are fed into the side armextruder (204) in a batch, liquefied, and then injected by means of apump into the planetary roller part (202).
 21. A method for producing ablend of plant particles and plastic particles in an extrusion line thatincludes a feed part (201), a side arm extruder (204), and at least oneplanetary roller part (202) that has a central spindle, multipleplanetary spindles, and a surrounding housing, with the multipleplanetary spindles rotating about the central spindle in the housing asa result of an internal toothing of the housing, said method comprisingthe steps of: feeding the plant particles into the feed part (201), amajority of the plant particles having a size of between 0.3 and 0.4 mmand the plant particles having a maximum size of 0.8 mm; feeding theplastic particles into the side arm extruder (204) and then,independently of the plant particles, liquefying the plastic particlesinto a plastic melt; advancing the plant particles out of the feed part(201) and into the planetary roller part (202); injecting the plasticmelt into the planetary roller part (202) with the plant particles, suchthat the plant particles have a proportion of at least 60% by weight inthe blend; blending and homogenizing the plastic melt with the plantparticles in the planetary roller part (202); and discharging the blendout of the extrusion line.